Hydraulic transmission mechanism



Aug 9; 1932- v F. H. sHEPARD, .JR 1,870,824

HYDRAULIC TRANSMI S S ION MECHANI SM Aug. 9, 1932. F. H. SHEPARD, JR ,1,870,824

` HYDRAULIC TRANSMISSION MECHANISM Filed Jan. 1o, 1929 4 sheets-she't 2 (N WS n HHI INVENTOR Franc/'s H Sheparaj Jr,

ATTORNEY Aug. 9, 1932. F. H. sHEPARD, JR 1,870,824

I yHYDRAULIC TRANSMISSION MECHNISM Filed Jan. 10, 1929 4 4 Sheets-Sheet 3 INVNTOR )v Franc/'5 Hheparol/r.

TTORNEY Aug. 9, 1932. F. H. sHEPARD, JR

Filed Jan. l0, 1929 4 Sheets-Sheet 4 l r. lll

INVENToR Franc/'5 H Shepard; ./f.

Patented Aug. 9, `19.32 f

. UNITED A s'rATEs,

ranuras H. SHEPARD, Jn., or NEW ROCHELLE; New Yoan mman-unici:rain-.rsiurssron mnc'namsm applicati@ ala January .10, 192e. semina. 331,629.

My invention relates, in general, to transmission mechanisms and, in particular, to hydraulic speed-changing transmission devices. Y Y

An object of my-invention is to provide a transmission mechanism which is capable o transmitting power between a-driving and a driven memberat any desired speed ratio within a predetermined. range.

Y l@ Another object of my invention is to prof vide a transmission device in which the speed ratio between thedriving andthe driven members may be automatically adjusted in response to the torque on the driven member.

ld A further object `o my invention vis' to -provide for utilizing a hydraulic pump toV control the speediratio between adriving and a driven member in order to obtain any desired speed ratio by changing the displace- -o ment volume ofthe pump. i

It is also an object of the invention to provide for controlling the volumevof fluid delivered by a pump without varying the pump speed, thereby to control the speed of thel transmission system.

Heretofore, it has been customary to effect 'changes in speed between a driving and a f driven member by means ofa gear reduction mechanism. As is wellknown, such gear reduction vmechanisms are objectionable -in that they are limited -to a small number of e speed ratios and the speed .ratio cannot be changed without disconnecting the driving member from the transmission mechanism By means of my invention, I provide a speed. changing device which may be adjusted to any desired speed ratio, within certain limits, while it is transmitting power.

rlfhe foregoing and other ob] Figure 1 1s aview, partlyinelevation and J partly in longitudinal section, of a hydraulic transmission mechanism, taken along the line I--I of Figs. 3 and 4, v v

Fig. 2 is a similar view, showing the movable; parts of the transmission mechanism in a diferenhposition. Y i

l ects of my in? 'J vention may be accomplished by means of- Fige is a view, in transverse section, of the transmission mechanism, taken along the Ime III-III of Figs. 1 and 2, and

Fig. 4: is another view, in transverse sec' along the line lV-IV of Figs.`

tion, taken 1 and 2.

Figs. 5 andv are sectional views of two l operative positions of a. detail, taken on a- .sectional plane substantially at right angl to the drawings in Fig. 1. f

Fig. 7 is a plan view of the sectional detail shown in Figs. .5 and p6.

Referring particularly toFigs. l and 2, the transmission mechanism embodying my invention comprises, in general, a speedreduction device 1, which isdisposed to transmit power, at a variable speed ratio, -from a' /driving shaft or member 2 to a` driven or output sha-ft 3,. which extend from opposite ends, respectively, of a protective casing d that is disposed to completely enclose the #speed-reduction mechanism 1` ln order t@ effect Aa change in speed between the driven member 3 and the driving.A

member 2, the speed-reduction mechanism 1 is provided with a. hydraulic-transmission system that comprises a. variable-volume pump 5 and a constant-volume pump 6 which are connected by, and constitute parts of,-a closed hydraulic circuitp?.

Each of the pump mechanis s 5 and 6 is Irovidedwith two interactildg elements.

ne element of each pump comprises a, luf.-

rality of pinions 8 and 9 which are carrie byv the driving member 2. The other elementof 'the variable-volume pump 5 comprises an annular gear member 11 that is normally held stationaryrelative tothe casing 4. The second element of the constant-volumepump 6 comprises a spurgear wheel 12 that 1s connectedk to the driven member 3. As a general proposition, inasmuch as the elements 8 and 9l of each of the pumps 5 and 6 are driven and the second element 11 of the pump 5 is held stationary, any chan e in the volume ofthe fluid being circulate within the closed circuit 7 will necessarily'change therelatlon of the speed of the driving member' 2 tothe y Speed 0f the other pump element-12 and-the driven member 3.' g .e

As shown in the drawings, the gear wheel 12, which constitutes part ofthe constantshaft 3, is dlsposed Awithin a spider member 13 which is mounted on the driving shaft 2 and 9.

Referring particularly to Fig. 3, it will be readily seen that the pump 6 comprises threepinions 9 that are j ournalled in the spider '13 upon arbors or pins 14 which are disposed 120 from each other. As shown, the spider 13 is provided-withsemi-cylindrical openings or' chambers 15 for receiving the pinions 9 in such manner that the teeth of the pinions closel'yengag'e the wall defining the opening 15 in order thatv the fluid being pumper may not pass from o ne tooth space tothe next.

The pinions Suof'the variable-volume pump are also journalled in the spider 13, upon suitable arbors 14, in suchmanner that they radius, has'a small number of teeth relative mesh with the annular gear wheel 11.

As shown in Fig. r3, the pinions 8 are disposed 120o from each other and are equally spaced between the pinions@ within semicylindrical openings 16. From Fig. 3, it may be readily seen that the spider 13 and the pinions Sand 9 are spXdisposed that they constitute a mechanically \J balanced rotating member. Further, it is obvious that any radial hydrostatic forces that may be set up within either the pumpc5 or the pump 6 are substantially balanced. f As shown in- Figs. 1 and 2, the pinions 9 are of a greater A length than the pinions 8,

for the reason that the'gear wheel 12, with which the p'nions 9 mesh, being of .small to the annular gear wheel 11and, therefore,

. in order that the volumes :of the pumps 5 and 6 may be substantially equal, it is necessary that the pinions 8.

For supporting the spider 13, the casing 4 is provided with an end plate 21 having a.

centrally disposed journal bearing 22 that receives a journal formed on one end of the spider 13. Ihe other end of the spider 13 is providedv with an-.end plate 23, a portion of which constitutes ajournal that is disposed toturn within a bearing 24 in an end plate 25 that constitutes the other end of the casing 4.

'By reason of the fact that the poinion's8 are relatively short, it is necessary to provide end plugs 26 that are inserted within those por-- tions of the cylindrical openings 16 which are not occupied by the pinions 8 and serve to support the corresponding ends of the arbors 14. For transmitting power to the spider 13', thedriv-ingshaft 2 is securely fastened within vthe journal portion on the end thereof by means ofv a key 27. The driven shaft 3, which receives power from the gear wheel 12,- issecurely fastened thereto by' and serves to support the pump elements 8 To provide means tor supporting the anpinions 9 be made longer .than the Vvmeans of a key 28 andextends through a journal bearing 2 9 which is disposed'within the journal portion of the end-plate member 23.. Each of the shafts 2 and 3 is provided withan oil thrower31' that is disposed to prevent fluid from leaking from the casing 4 and to return such as may leak through the bearings 22, 24 and 29 to a'sump 32 in the bottom of lthe casing 4 by means of ducts 33.

As shown in Fig. 3, the transmission ilu-id passes from'the pump 5 tothe pump 6 and back to the pump 5 again through passages 35 which constitute parts of the closed hydraulic circuit 7 By reason of the compact construction of the speed-changing device,-

the passages' 35 are made -relatively large and constitute a direct hydraulic connection between the two pumps, whchis of suicient cross sectional area to enable the fluid `to be 4transmitted without serious friction losses.

nular gear wheel 11, whichconstitutes. part of the pump mechanism 5, thespeed-reduc` ing device is encircled by an annularghousing or gear-rim'holder 41 intowhich the annular gear 11 may be pressed rotherwise secured. For the purpose of.I holding the gear rim 11 stationary, relative to the casing-4, the

i gear-rim holder 41 isprovided, at one end,

with'a cylindrical surfa'e or brake drum V42 which isdisposed to be engaged by a brake Aband -43 of well known construction. order to transmit the reaction torque of the annular gear 11 to the casing' 4, a torque-reaction ring 44 is provided. The torque-reaction ring 44 is secured to the brakeband 43 in any'suitable manner, preferably in such manner that it exerts substantially no radial force upon the brake drum 42.

-Figs. 5, 6 and 7 show one method 4ot' securing the ring 44 tozthe band 43. The band 43 is provided withthe ears 101 having slots 102. A pin 100' mounted -onthearm 103 rigidly secured to ring 44 ts loosely in the' V slot 102. The cooperative action of the pin and slot is such that the arcuate movement of the ring 44 about ball joint 45 does -not .interfere with the rectilinear movement of i the band 43. Y In .order that'the volumetric displacement or pumping capacity of the pump 5 may be readily varied, the gear-rim holder 41 is so mounted on the spider 13 that it may be moved longitudinally thereonfin such manner that the face of. the annular gear 11 may be displaced axially, relative vto the faces of the pinions 8. -The axialdisplacem'ent of the gear-rim holder 41 ismade possible byreafl son of the fact .that the torque-reaction ring 44 is pivoted by means of a-lball joint 45 in -the bottomof the casing 4 and is'provided,

at'its upper end, with a shifting lever 46 which extends through an opening 47 in the f top ofthe casing4 that is closed-by a sl able cover plate 48. It may be readily see that,

i by simply moving the lever 46 in a direction parallel to the axis of the transmission mechanism to the position shown inFig. 2, the housing 41 and the annular gear 11 may be moved am'ally relative to the spider 13 and the pinions 8 .by reason of the'connection between the torque-reaction ring 44 and the brake band 43.

Further, when the face of theannul-ar gear 11 is displaced axially relative to the faces of the pinions 8, the eiective length of the teeth in contact is thereby reduced and coni sequently, the volume displaced by each tooth of that portion of the teeth of the pinions 8, whichare e osed by reason of the axial displacement o the annular gear 11, a battle ring 51 is provided within the gear-rim holder 41 and adjacent to the annular gear 11.`

The baiiie ring 51 is disposed to rotate with the spider 13 and is provided, on its inner surface, with depressions having concave surfaces which snugly engage the outer surfaces of the pinions 8. Asshown in Fig. 1,

the baiiie ring 51 is so mounted within the gear-rim holder 41 thatV it maintains close engagement with the ends of the teeth of the annular gear wheel 11 and with the tips of the t`eeth of the pinions 8 insuch manner that leakage of the transmission .fluid at the exposed tips of the teeth of the'pinions 8 is eii'ectually prevented.

In order to prevent leakage of-fluid around the exposed ends of the teeth of the pinions 8, a packing blank 52, which is complementary in shape'to the annular gear wheel 11, is disposed around the circumference of the spider 13 in such manner thatit completely ills the spaces between the teeth of the annular gear 11. -For the purpose of positively sealing the packing blank 52, its surface farthest from' the'teeth of the pinions 8 is provided with a washer 50 of leather or other suitable packing material which acts as a valve to prevent the flow of transmission fluid from the portion ofthe annular gear 11 which is out of engagement with the pinions 8. Such transmission kf iuid as may leak from the speed-reduction mechanism is collected in theV sump 32 in the bottom of the casing 4 and may be returned to the act-ive system by means of any suitable pump (not shown) which is disposed to withdraw the fluid through a pipe 54 andforce it into the journal bearing 22 from which it is conducted, through passageways 55 and 155 within the driving shaft 2, and the vpassageway 55 in the spider 13,- to the-low-pressure side of the pump l6. .Y

As may b e readily seen'by referring to Fig. 2, when the gear-rim holder 41 is moved to theleft outl of engagement with the .packing blank 52, the pressure of the transmission fluid which is inthe space between the ends of the teeth on the pinion 8 and the radial wall of the gear rim holder 41 has a tendency to force the -ear-rim holder 41 towards the left.. m To provi e means for counteractino`- this unbalanced hydrostatic force, the lright-hand end of the'gear-rim holder 41 is provided with a pressure/balancing ring 56. The ring 56 is provided With slots on its inner surface '36 which are disposed to engage tongues 57 on the outer faces of the end plugs 26. A. washer or lining 60 of leather or other suitable. materi'al is provided on the surface of the ring 56, adjacent to the balie ring 51, to prevent aai leakage. As shown, the faces of the end plugs 26 which are in engagement with the ends ot the teeth of the plnions 8, present circular baiie walls which are pierced by passagewaye- 58 at the sides of the Atongues 57. The pas- 65 sageways 58 admit fluid, under pressure, from between the teeth of the pinions 8 into cha-1nbers 59 which are formed between the solid ends of the plugs 26 and that portion of the pressure-balancing ring 56 which is adjacent 950 to the tongues 57. e It may be readily seen that, by properly selecting the area of the exposed portion of thepressure-balan'cing ring 56, the resultant hydro-static pressure acting upon the gear-rim holder may be reduced to a5 zero `or to some other value which may be lfound to be advantageous.y

When the annular gear Wheel 11 is fully engaged with the pinions 8, the output of the pump 5 yis greater than the output of the me pump 6 and, consequently, by reason of the fact that the pumps are connected by a closed hydraulic circuit lwhen, the transmission mechanism is in operation, the .pump -6 mu rotate faster than the pump 5 in order to co 105 pensate for `the dierence 1n volume displacement. By moving the ring v'gear wheel 11 to the left to a predetermined position, the volume displacement of the ump 5 may be made equal to the volume displacement of 110 the pump 6. When the speed-reduction mechanism is'adj usted in this manner and the gear rim. 11 is held stationary by means of the brake ba-nd 43, the gear wheel 12 will also remain stationary when-the spider 13 is ro- 115 Y element 11 and the ygear element 12 are stationary relative to the heusing 4 and,'there fore. it may be said that the speed of the .125

driven shaft 3, relative to the gear wheel 11,

-is zero. l

-AS Shown' in Fig- .fhe hydraulic oircui 7 is so .Connected that when the output of the Y Pump 5: is made grea'ter than the output of the so pump 6, the gear wheel 12 will be caused to rotate, relative to the gear-wheel 11, in a direction opposite to the direction of rotation of the spider 13, in order that the additional volume of iuid expelled by the pump 5 may be transmitted through the pump 6. When volumetric displacement of .pump 5 is reduced, the gear wheel 12 and the driven mem-` ber 3 will be carried in a predetermined direction, while the spider 13`and the fluid pressure developed by the pump 6 will be ex- `crted upon the pump 5 in such manner that it will addto the torque supplied to the spider 13 by the driving shaft 2. When rotating in this direction, the total torque on the input or driving shaft 2 is transmitted directly, by means of the pump 6, to the driven or output shaft 3, and a ditional or feed-back torque is also exerted pon the driven shaft 3 by reason of' the fact that` the pump 6 drives\the pump V5 as a hydraulic motor. It may be readily seen that, if the volumetric displacement of the pump 5 (which is now acting as a hydraulic motor) is further reduced, the

speed ofthe shaft 3 will be increased, and a greater percentage of the torque on the shaft 3 will be transmitted directly from the input or driving. shaft 2.

If, now, the annular gear wheel 11 is moved entirely out of engagement-with the inions 8 to the position shown in Fig. 2, an the output of the hydraulic motor 5 is 'thereby reduced to zero, then the relative velocity between the .gear wheel 12 and the lcooperating pinions 9 of the pump 6 will also be reduced to zero, and the driven shaft 3 will rotate at substantially the speed of the driving shaft 2.

When this condition of hydraulic lock occurs, it may be desirable to connect the driving shaft directly to the driven shaft 3 by mechanical means, in. order that 'the speedreduction mechanism may be relieved from all work, and thepressure ofthe transmission iuid reduced to substantially zero. In

order to accomplish this result, the drivenshaft?, is providedwith a clutch member 61 v which is disposed to engage acooperating clutch. member. 62 on the spider-end-plate member 23.I

A shifting lever 63 is provided for engaging the clutchl members inthe usual wellknown manner. Afteil-thc clutch .members 61 and 62 have been engged,the annular gear stantially 100%.

wheel 11 and its supporting member 11 may be released by loosemng the brake band 43 in order that they may turn with the spider 13 and consequently, the entire speed-reducing mechanism 1 will rotate as a unit without relative movement'between its various parts.

It may be readily seen that, when the transmission mechanism is operating at a one-toone ratio in this manner, its eflic'iency is sub- -When operating at any other speed ratio in the forward direction, as hereinbefore described, only a portion of the ower being transmitted passes through the iydraulic system, the remainder being transmitted directly to the driven shaft 3 by reason ofthe fact that the torque of the driving shaft 2 is exerted directly upon the gear wheel 12 and the total torqueltherefore, 1s equal to the torque exerted by t e driving shaft 2 upon the spider 13 and the pinions 9 plus the torque exerted b the hydraulic pressure on the pmions 9. of the transmission mechanism is equal tov the eiciency loss of the hydraulic system multiplied by the percentage of the total power which is being transmitted by the hydraulic system.

If itis desirable todo so, the speed-changing device 1 may be -made to operate auto-A matically in response to the torque on the driven shaft 3. It is evident that the pressure in the hydraulic systemV is in direct proportion to the torque being exerted b the pinions 9 upon the gearwheel 12. ence, itis a simple matter to so proportion the onsequently, the total eiiciency loss v balancing areas on the balancing ring 56 that a biasing force will be exerted which tends to increase the output of the pump 5 by moving the annular gear wheel 11 towards the right. This biasing force may be offset by means of a compression spring 65 which exerts a force upon the shifting lever 46 by reason of its engagement with the lsliding plate48 in such manner as to oppose the tendency of the pressure on the balancing areas to shift the housing 41 to the right.

Suitable means, such as a hand wheel 66, may be provided for adjusting the compression of thespring 65-and, consequently, adjusting the torque on the driving of input shaft 2. It may be readily seen that, as the torque necessary to turn the driven shaft 3 becomes greater, the pressure in the hydrau- 1i c system will'increase and exert a force upon the balancing 4ring 56 which will shift the gear wheel 11 to the right in opposition tc the biasing spring 65. Moving the gear wheel to the right will increase the capacity-of the hydraulic motor 5 and, consequently, reduce the speed, as well as increase the torque, exl erted upon the driven shaft 3 without ma.- terially changing the Vtorque necessary to4 be applied to the driving shaft 2.

Although I have described a particular embodiment of my invention, it will be clear to those skilled in the art that various modifications may be made in the design of the detail parts ofthe transmission mechanism and their dis osition relative to one another without. eparting from the spirit and scope of the invention, as defined in the appended claims. i

I claim as my invention:

1. In a hydraulic transmission mechanism, in combination, two pump mechanisms, one comprising an annular gear wheel and a plu'- rality of cooperating pinions and the other comprising a spur gear wheel and a plurality of cooperating pinions, driving means for actuating the pinions, a closed liydrauliccircuit for connecting the two pump mechanisms, a driven member connected to the spur gear wheel, means for holding the annular gear wheel stationary, and means for varying the output of the first pump mechanism to change the ratio between the driving means and the driven member, said means comprising mechanism for moving the ring gear wheel relative to its meshing pinions.

3. In a hydraulic transmission mechanism,

in combination, two pump mechanisms, one comprising an annular gear wheel and a plurality of cooperating pinions and the `other comprising a spur gear wheel and a plurality of cooperating pinions, driving means for actuating the pinions, a closed hydraulic circuit for donnecting the .two pumpmechanisms, a driven member connected to the spur gear wheel, means for holding the annular gear wheel stationary, means for varying the Y output of the irst pump-mechanism to vary the ratio between'the driving means and the driven member, means for releasing the annular gear wheel, and means for mechanically connecting the driving means to the driven member.

i. A hydraulic transmission comprising a driven member, a gear wheel carried by the driven member, a driving member, a spider carried by the driving member, a gear wheel journalled in the spider for meshing with the gear wheel on the driven member to cona, stitute a hydraulic pump, an annular gear wheel encircling the spider, a second gear wheel journalled in the spider for meshing with the annular gear wheel to constitute a second hydraulic pump, and a closed hydraul ,l Y

lic circuit for connecting the two pumps.

` 5; A hydraulic transmission mechanism comprising a driving member, a spider carried by the driving member, a gear wheel to disposed within the spider, a driven element secured to the gear wheel, an annular gear wheel disposed to encircle the spider, pinions journalled in the. spider for engaging the gear wheel to constitute a pump mechanism,

other pinions journalled in the spider for engaging the annular gear wheel to constitute a second pump mechanism, and a closed hydraulic circuit for connecting. the two pump' mechanisms.

6. A hydraulic transmission mechanism comprising a-driving member, a spider carried by the driving member, a gear wheel disposed within the spider, a driven element sei cured to the gear wheel, an Iannular gear '85 4 wheel disposed to encircle the spider, pinions 'journalled in the spider for engaging the gear wheel -to constitute a pump mechanism, other pinions journalled in the spider for engaging the annular gear wheelto constitute W a second pump mechanism and a closed hydraulic circuit for connecting the two pump mechanisms, and means for varying the output of one of the pump mechanisms to vary the ratio of the speed of the driving member @E to the driven member.

v 7. A hydraulic transmission mechanism. comprising 'a driving member, a spider car'- ried by the driving member, `a gear wheel Y disposed within the spider, a driven element N@ secured to the gear wheel, an annular gearwheel disposed to encircle the spider, pinions journalled in the spider for engaging the gear wheel toconstitute a pump mechanism,

other pinions journalled in the spider for en- 1M gaging the annular gear wheel to constitute s a second vpump mechanism, a closed hydrau lic circuit for connecting the two pump mech- ,anisms and means for moving the annular to vary the output of one n@ gear wheel. axially of the pump mec anisms, whereby the speed v ratio between the. driving and the `driven vshaitts maybe varied. v l

8. A hydraulic transmission mechanism comprising a driving member, aspider carum ried by the driving member, a gear wheel disposed within the spider, a driven element se-l cured to the gear wheel, an annular ear wheel disposed to encircle the spider, pinions journalled in the spider for engaging the m@ gear wheel to lconstitute a pump mechanism, other pinions j ournalled in the spider for engaging the annular gear wheel to constitute a second pump mechanism, a closed hydraulic circuit for connectingthetwo pump mechanisms, and means responsive to the pressure in the hydraulic circuit for moving the an-V nular gear wheel relative to its cooperating pinion to vadjust thel capacity of the pump mechanism and thereby automatically regu- 1 late the ratio of the speed of the driving memb'er to the driven member in response to the torque of the driven member.

9. A hydrauli transmission mechanism 5 comprising `a driving element, a spider mounted o'n the driving element, a plurality of pinions rotatably mounted in the spider,

an annular gearvrimfor engaging the pinions to constitute a gear hydraulic pump,

T10 means for preventingthe annular gear ring from rotatm means for varying the axial position of t e annular gear rim to adjust the rate of pumping of the gear pumps, a second set of pinions rotatably mounted in 15 the s ider, a driven element, a gear wheel on the riven`.element for engaging the second set of inions in the'spider to constitute a .hydra 'c motor, and means for transmittin Huid from the pum to the motor. -20

testimony whereof, have hereunto subscribed my name this4th day of' J anuary,

FRANCIS H. SHEPARD, Jn. 

